Disease management strategies are very
similar for both organic and conventional small fruit production
systems in the Midwest. In both systems it is important to develop and
use an integrated disease management program that integrates as many
disease control methods as possible, the more the better. Major
components of the disease management program include: use of
specific cultural practices; developing knowledge of the pathogen and
disease biology, use of disease resistant cultivars, and timely
application of organically approved fungicides or biological control
agents or products when needed. These guidelines have been written
for caneberries (raspberry and blackberry), strawberry, blueberry and
grape. Specific information is provided for each crop in its respective
chapter. Most disease control methods or strategies are identical for
both conventional and organic production systems. Perhaps the greatest
difference between organic and conventional production systems is that
organic growers are not permitted to use synthetic "conventional"
fungicides. If disease control materials are required in the organic
system, growers are limited to the use of "inorganic" fungicides such
as sulfur (elemental sulfur and lime-sulfur) or copper fungicides
(Bordeaux mixture and fixed copper products). In addition, there are
several new "alternative" disease control materials and biological
control products that are currently available and are cleared for use
in organic production.
There are several problems associated with
the use of these inorganic fungicides and "alternative" products in
small fruit disease control programs. Among the most important are 1) Phytoxicity,
which is the potential to cause damage to foliage, fruit set and fruit
finish (this is a concern primarily with copper and sulfur fungicides);
and 2) their limited spectrum of fungicide activity, which
means they may not be capable of providing simultaneous control of the
wide range of fungal pathogens that can cause economic damage to the
crop. For example, sulfur is highly effective for controlling powdery
mildew on most fruit crops, but provides little or no control of most
In a climate like the Midwest, environmental
conditions during the growing season are generally very conducive (warm
and wet) to the development of several important diseases, insect pests
and weeds. Limitations in relation to which pesticides may or may not
be used, present the organic grower with some unique and very demanding
challenges. Whereas the use of various cultural practices and disease
resistance will be the "back bone" of the organic disease management
program, the limited use of organically approved pesticides or
biocontrol agents will probably be required at times.
Integrated Management of Bramble
An integrated disease management program
for controlling raspberry and blackberry diseases integrates the use of
all available control methods into one program. The use of organically
approved fungicides or biological control agents for control of several
important diseases can be a major part of the overall disease
management program, but the use of various cultural practices is
perhaps even more important in obtaining effective disease control. An
effective disease management program for brambles must emphasize the
integrated use of specific cultural practices, knowledge of the
pathogen and disease biology, disease resistant cultivars, and timely
applications of organically approved fungicides or biological control
agents or products when needed.
The objective of the disease management
program is to provide a commercially acceptable level of disease
control on a consistent (year-to-year) basis, with minimal fungicide
Identifying and Understanding the
Major Bramble Diseases
It is important for growers to be able to
recognize the major bramble diseases. Proper disease identification is
critical to making the correct disease management decisions. In
addition, growers should develop a basic understanding of pathogen
biology and disease cycles for the major bramble diseases. The more you
know about the disease, the better equipped you will be to make sound
and effective management decisions.
The following literature contains color
photographs of disease symptoms on brambles as well as in-depth
information on pathogen biology and disease development. These
publications also contain excellent color photographs and information
about insect pests as well.
Compendium of Raspberry and Blackberry Diseases
Published by the American Phytopathological Society, 3340 Pilot Knob
Rd., St. Paul, MN 55121. Phone: 612-454-7250. (1-800-328-7560). This is
the most comprehensive book on bramble diseases and insects available.
All commercial growers should have a copy.
Bramble Production Guide
This is a comprehensive book covering most phases of bramble
production. It can be purchased from: Northeast Regional Agricultural
Engineering Service, 152 Riley-Robb Hall, Cooperative Extension,
Ithaca, NY 14853. Phone: 607-255-7654.
Brambles: Production, Management and Marketing
The following information gives a description of
symptoms and causal organisms for the most common raspberry and
blackberry diseases in the Midwest.
Bulletin 783 of Ohio State University Extension, can be obtained from
Ohio State University Extension Publications Office, 385 Kottman Hall,
2021 Coffey Rd., Columbus, OH 43210-1044. Phone 614-292-1607
Cane and Leaf Diseases
Anthracnose is caused by the fungus Elsinoe veneta. One of the
most common and widespread diseases of brambles in the United States,
anthracnose can infect red and black raspberries, blackberries,
dewberries, and loganberries. The disease is very destructive on black
and purple raspberries. On red raspberries, it can be common but is
usually not a serious problem. Disease losses can occur from
defoliation, general stunting and a decrease in cane vigor, reduction
in fruit yield and quality, and cane death. Resistance to anthracnose
is not available in most varieties. The use of fungicide (lime sulfur)
and cultural practices such as sanitation (removal of old and infected
canes) are key control methods.
Anthracnose can cause symptoms on canes, leaves, fruit and stems of
berry clusters. The most striking symptoms are on canes. A few days
after the fungus invades the succulent tissue of young canes, minute
purplish spots appear. These spots enlarge in diameter and become oval
or lens-shaped. The centers become somewhat sunken and are pale-buff to
an ash-gray color (Figure 27). Margins are somewhat raised and purple
to purple-brown. If numerous, the lesions may merge and cover large
portions of the cane. Diseased tissue extends down into the bark,
partly girdling the cane. As the canes dry in late summer and early
fall, diseased tissue often cracks. In the following year, fruit
produced on severely diseased canes may fail to develop to normal size
and may shrivel and dry, especially in a dry growing season.
Figure 27: Anthracnose lesions on black raspberry canes.
On leaves, anthracnose appears on the upper surface in
early- to mid summer as irregular, yellowish-white spots about 1/16
inch in diameter (Figure 28). The spots gradually enlarge and develop a
reddish-purple margin around a light-gray center. The centers of these
spots may drop out, producing a "Shot hole" effect. This "Shot hole"
symptom is more common on trailing blackberries and raspberries. On
blackberries, leaf spots may merge together producing large grayish
dead areas between the veins. Anthracnose does not usually cause much
damage to leaves of erect blackberries.
Figure 28: Anthracnose leaf symptoms on black raspberry.
The anthracnose fungus overwinters in the bark or within lesions on
infected canes (Figure 29). In early spring the fungus produces two
types of microscopic spores called conidia and ascospores. Conidia,
which are produced in small fungal fruiting structures called acervuli,
are the most common form of inoculum. Ascospores are comparatively
rare. Production of these spores coincides with the leafing out of
brambles in early spring. Spores are rain-splashed, blown, or carried
by insects to young, succulent, rapidly growing plant parts that are
susceptible to infection. The spores germinate in a film of water and
penetrate into the plant tissue. Symptoms appear about a week later.
Small pimple-like reproductive bodies are produced within lesions on
infected canes and the fungus overwinters there. These bodies produce
conidia for new infections the next spring, completing the disease
cycle. As canes age and harden, they become much less susceptible
Figure 29: Anthracnose disease cycle. Disease cycle of
Raspberry Anthracnose. Taken from the Compendium of Raspberry and
Blackberry Disease and Insects of the American Phytopatholical Society.
Used with permission.
Cane blight is caused by the fungus Leptosphaeria coniothyrium. Cane
blight is one of the more damaging diseases of raspberries. The disease
is most common on black raspberries, but also occurs on red and purple
cultivars. Cane blight occasionally occurs on blackberries and
dewberries. Cane blight can result in wilt and death of lateral shoots,
a general weakening of the cane, and reduced yield. It is usually most
severe during wet seasons. The fungus often invades the cane through
wounds. Any practice that reduces wounding on canes is beneficial for
control. Key control methods are the same as for anthracnose.
Dark brown to purplish cankers form on new canes near
the end of the season where pruning, insect, and other wounds are
present. The cankers enlarge and extend down the cane or encircle it,
causing lateral shoots to wilt and eventually die (Figure 30). On
second-year canes, the side branches may suddenly wilt and die, usually
between blossoming and fruit ripening. On close examination, dark brown
or purplish cankers can be observed on the main cane or branches below
the wilted area. Infected canes commonly become cracked and brittle and
break easily. Tiny black specks (pycnidia), which are reproductive
bodies of the cane blight fungus, develop in the brown cankered bark.
In wet weather, large numbers of microscopic spores (conidia) ooze out
of the pycnidia. This ooze gives the bark a dark-gray, smudgy
Figure 30: Cane blight lesion on thornless blackberry.
The pathogen survives over winter on infected or dead
canes (Figure 31). The following spring, conidia, formed in the
pycnidia, ooze from them during wet periods, and are blown, splashed by
rain, and carried by insects to nearby canes. Under moist conditions,
the spores germinate and penetrate into the plant through pruning
wounds, insect punctures, fruit stem breaks, and other wounds. After
entry, the fungus rapidly invades and kills bark and other cane
tissues. Pycnidia are formed in older cankers and complete the disease
cycle. Dead canes can continue to produce conidia and remain a source
of infection for several years.
Figure 31: Cane blight disease cycle. Taken from the
Compendium of Raspberry and Blackberry Diseaes and Insects of the
American Phytopathological Society. Used with permission.
Blight of Red Raspberries
Spur blight is caused by the fungus Didymella applanata. Spur blight
occurs only on red and purple raspberries. Spur blight has been
considered to be a serious disease of red raspberry; however, recent
studies in Scotland suggest that spur blight actually does little
damage to the cane. The extent of damage caused by spur blight in the
United States is not clearly understood. Key control methods are the
same as for anthracnose and cane blight.
Symptoms first appear on young canes in late spring or
early summer. Purple to brown areas (cankers) appear just below the
leaf or bud, usually on the lower portion of the stem (Figure 32).
These cankers expand, sometimes covering all of the area between two
leaves. In late summer or early fall, bark in the cankered cane area
splits lengthwise and fungal fruiting bodies, appearing as small black
specks, develop in the cankers. They are followed shortly by the
formation of many slightly larger, black, erupting spots, another form
of fungal fruiting body. Leaflets sometimes become infected and show
brown, wedge-shaped diseased areas, with the widest portion of the
wedge at the top of the leaf. Infected leaves may fall off, leaving
only petioles without leaf blades attached to the cane (Figure 33).
Figure 32: Typical symptoms of spur blight on red
Figure 33: Symptoms of spur blight on red raspberry
leaves. The "V-shaped" lesions are characteristic.
As diseased primocanes become fruiting canes (floricanes) during the
next season, the side branches growing from diseased buds are often
weak and withered and produce less fruit.
The fungus survives the winter in diseased canes (Figure 34). The
following spring and summer, during wet and rainy periods, spores are
released and carried by splashing rain and wind to nearby new growth.
There they germinate and produce new infections, where the fungus will
Figure 34: Spur blight disease cycle. Taken from the Compendium of
raspberry and Blackberry Diseases and Insects of the American
Phytopathological Society. Used with permission.
Leaf and Cane Spot
Septoria leaf and cane spot is caused by the fungus Septoria
rubi. The disease is common and can be quite severe in the southern
portions of the Midwest on erect and trailing blackberries and black
raspberries. Leaves and canes of severely infected plants become badly
spotted. The disease can cause premature defoliation which will produce
weak plants that are more susceptible to winter injury.
On leaves, Septoria leaf spot lesions have a whitish to
gray center surrounded by a brown to purple border (Figure 35). The
spots are circular and are about 1/8 inch in diameter. Tiny black
pycnidia (fungal fruiting bodies) form in the center of the spots. The
pycnidia are small; therefore, it may be necessary to use a magnifying
glass (10X hand lens) to see them. Leaf spots caused by Septoria are
similar to those of anthracnose. Spots on canes and petioles are
similar to those on leaves but are generally more elongated.
Figure 35: Septoria leaf spot on blackberry leaflet.
The fungus overwinters as mycelium and pycnidia (fungal
fruiting bodies) in dead plant debris (leaves and stems) and on
infected canes. Pycnidia on infected canes from a nursery can be an
effective means for moving the fungus into new fields. In the spring,
spores (conidia) are produced inside the pycnidia. They are released in
high numbers and carried to young susceptible leaves and canes by
splashing or wind-driven rain. The fungus spores germinate in a film of
moisture and penetrate the leaf or cane tissue. As leaf and cane spots
form and age, new pycnidia form in the centers. These also produce and
release spores that can cause secondary infections throughout the
growing season. Although the environmental conditions required for
infection are not clearly understood, periods of rainfall are highly
conducive to disease development. After overwintering in infected canes
or debris, the fungus produces spores for new infections the following
spring, completing the disease cycle.
Rosette, or double blossom, is caused by the fungus Cercosporella
rubi. Rosette is a serious disease of many varieties of erect and
trailing blackberries, particularly in the humid southern United States
and the southern regions of the Midwest. The disease is not present in
the more northern regions of the Midwest. Rosette also occurs on red
and black raspberry but is seldom serious. Rosette infected blossoms do
not form berries and non-infected parts of the same cane may produce
poor quality fruit. The disease seriously reduces fruit quality and
yield. Once the disease is established in organic plantings, little can
be done to control it.
Symptoms of rosette disease are striking and may
completely change the plants' appearance due to a proliferation of
shoots. This proliferation of shoots is referred to as a witches'
broom. Buds on new canes of erect and trailing blackberries are
infected in early summer. Generally, no symptoms will develop until the
following spring, although a few "Witches' brooms" may develop during
warm spells in late fall. In the spring, numerous leafy sprouts develop
from infected buds (Figure 36). These shoots are generally smaller than
normal and have pale green foliage that later turns a bronze color.
Several of these witches' brooms may be formed on one cane. Unopened
infected flower buds are abnormally large and coarse and frequently
somewhat redder. Sepals enlarge and occasionally change into leaves.
Flower petals may become green and leaflike. As flower buds open,
petals are usually pinkish in color, wrinkled and twisted. Pistils are
usually larger and longer than normal and occasionally become
abnormally shaped. The fungus produces a whitish spore mass that can
cover the surface of the infected pistils and stamens. Berries do not
develop from infected blossoms. Non-infected parts of the same cane
often produce small, poor quality fruit. In some varieties the witches'
brooms symptoms may not be apparent; however, the fruit set in infected
blossoms is always impaired.
Figure 36: Symptoms of rosette disease on blackberry.
Young buds on vegetative canes are infected in early
spring (Figure 37). The double blossom fungus grows between the bud
scales and surrounds the embryonic tissues within the bud. As secondary
buds develop beside an infected bud, they are also invaded. After the
bud is colonized by the fungus, very little happens. Infected buds
usually remain symptomless until the next spring. A few infected buds
are sometimes forced out in an unusually warm late fall. The fungus
overwinters in infected buds. During the winter the fungus continues to
grow within the bud. Bud proliferation is induced. When infected buds
break dormancy in spring, they develop a large number of short,
abnormal and off-colored shoots (the witches' broom effect). Infected
flower buds usually produce abnormal blossoms upon which the fungus
produces its spores. These spores are carried by wind or insects to the
newly formed vegetative buds, which are only susceptible to infection
in early spring. The fungus infects these buds and overwinters in them
to cause new symptoms the next spring, thus completing the disease
Figure 37: Disease cycle of rosette. Taken from the
Compendium of Raspberry and Blackberry Diseases and Insects of the
American Phytopathological Society Used with Permission.
Powdery mildew is caused by the fungus Sphaerotheca macularis. Powdery
mildew affects susceptible cultivars of red, black, and purple
raspberries. Blackberries and their hybrids are usually not affected.
The disease can be severe (varying from year to year) on highly
susceptible cultivars, and these plants may be stunted and less
productive. The infection of flower buds reduces fruit quantity.
Infected fruit may be lower in quality or unmarketable as a result of
the unsightly covering of mycelial growth. The key control method is to
avoid susceptible varieties. Sulfur will provide good control on
Infected leaves develop light green blotches on the
upper surface. Generally, the lower surface of the leaf directly
beneath these spots becomes covered by white, mycelial growth of the
powdery mildew fungus. The leaf spots may appear water-soaked. Infected
leaves are often mottled, and if surface growth of the fungus is
sparse, they often appear to be infected by a mosaic virus. Infected
shoot tips may also become covered with mycelial growth (Figure 38).
When severely infected, the shoots become long and spindly
(rat-tailed), with dwarfed leaves that are often curled upward at the
margins (Figure 39). Infected fruit may also become covered with a
white mycelial mat. When the disease is severe, the entire plant may be
Figure 38: Powdery mildew on blackberry leaves. Note the
leaves are covered with the white growth of the fungus.
Figure 39: Powdery mildew on blackberry. Note the
distortion of leaves.
The fungus overwinters as mycelium in buds on shoot tips
in Minnesota, but in California it has been reported to overwinter only
as cleistothecia (fungal fruiting structures), producing ascospores as
primary inoculum in the spring. Conidia are generally abundantly
produced on the surface of infected tissue, and these serve as
secondary inoculum for repeated cycles of infection throughout the
growing season. They are airborne and probably remain viable for no
more than 21 days. The development of this disease, like most other
powdery mildew diseases, is favored by warm, dry weather.
Orange rust is the most important of several rust
diseases that attack brambles. All varieties of black and purple
raspberries and most varieties of erect blackberries and trailing
blackberries are very susceptible. Orange rust does not affect red
raspberries. Orange rust is caused by two fungi that are almost
identical, except for a few differences in their life cycles. Arthuriomyces peckianus occurs
primarily in the northeastern quarter of the United States and is the
causal agent for the disease in the Midwest. Gymnoconia nitens is a microcyclic
(lacks certain spores) stage of A.
peckianus. G. nitens
is the more common rust pathogen on erect and trailing blackberries in
Unlike all other fungi that infect brambles, the orange
rust fungus grows "Systemically" throughout the roots, crown and shoots
of an infected plant, and is perennial inside the below-ground plant
parts. Once a plant is infected by orange rust, it is infected for
life. Orange rust does not normally kill plants, but causes them to be
so stunted and weakened that they produce little or no fruit. Key
control methods are cultural practices such as removing infected plants
early in the spring and eradication of wild hosts (brambles) near the
planting. Organic fungicides are not effective for control. In severely
infested areas, black raspberries or blackberries should probably not
be planted. Red raspberries are not susceptible.
Orange rust-infected plants can be easily identified
shortly after new growth appears in the spring. Newly formed shoots are
weak and spindly (Figure 40). The new leaves on such canes are stunted
or misshapen and pale green to yellowish (Figure 41). This is important
to remember when one considers control, because infected plants can be
easily identified and removed at this time. Within a few weeks, the
lower surface of infected leaves are covered with blister-like pustules
that are waxy at first but soon turn powdery and bright orange (Figure
42, 43). This bright orange, rusty appearance is what gives the disease
its name. Rusted leaves wither and drop in late spring or early summer.
Later in the season, the tips of infected young canes appear to have
outgrown the fungus and may appear normal. At this point, infected
plants are often difficult to identify. In reality, the plants are
systemically infected, and in the following years, infected canes will
be bushy and spindly, and will bear little or no fruit.
Figure 40: Black raspberry plants showing early season
symptoms of orange rust. Note the "Spindly" elongated shoots. Orange
pustules will develop on the underside of infected leaves.
Figure 41: Leaves on infected plants are usually yellow
(chlorotic) and smaller than leaves on healthy plants.
Figure 42: Orange rust symptoms on the underside of a
black raspberry leaf.
Figure 43: Close-up blister like pustules on the
underside of an infected black raspberry leaf. Pustules contain bright
orange masses of fungus spores.
In late May to early June, wind and perhaps rain-splash
spreads the bright orange aeciospores from the pustules on infected
leaves to healthy susceptible leaves where they infect only localized
areas of individual mature leaves (Figure 44). When environmental
conditions favorable for infection occur, the spores germinate and
penetrate the leaf. About 21-40 days after infection, small, brownish
black telia develop on the underside of infected leaflets. The
teliospores borne in these telia germinate to produce a basidium, which
in turn produces basidiospores. In blackberries these spores then
infect buds on cane tips as they root. They also may infect buds or new
shoots being formed at the crowns of healthy plants in the summer. The
fungus becomes systemic in these young plants, growing into the crown
at the base of the infected shoot, and into newly formed roots. As a
result, a few canes from the crown will show rust the following year.
The fungus overwinters as systemic, perennial mycelium within the host.
Figure 44: Orange rust disease cycle. Taken from the
Compendium of Raspberry and Blackberry Diseases and Insects of the
American Phytopathological Society. Used with Permission.
Orange rust is favored by low temperatures and high
humidity. Temperatures ranging from 43 to 72 F favor penetration and
development of the fungus, but higher temperatures decrease the
percentage of spore germination. At 77 F, aeciospores germinate very
slowly, and disease development is greatly retarded. Spore germination
and plant penetration have not been observed at 86 F. Aeciospores
require long periods of leaf wetness before they germinate, penetrate,
and infect plants.
Late leaf rust, caused by the fungus Pucciniastrum americanum, can cause
serious damage to susceptible red raspberry cultivars. Economic losses
occur from fruit infection and premature defoliation. Because it
usually appears late in the season and only occasionally in a severe
form, some consider it to be a minor disease. The wild red raspberry, Rubus strigosus, in the eastern
United States is very susceptible to this rust. A number of cultivars
originating from this species also are highly susceptible. While late
leaf rust occurs throughout the northern half of the United States and
southern Canada, it is more common east of the Mississippi River. In
recent years, its occurrence has increased in the northern areas of the
Midwest and it has caused significant losses. The rust does not occur
on black raspberries or blackberries. Organic fungicides are not
effective for control. Once established in the planting, little can be
done to control it.
On mature leaves, late leaf rust causes small chlorotic or yellow spots
to form on the upper leaf surface (Figure 45). These spots may turn
brown before leaves die in the fall. Unless the disease is severe,
foliar infections can be rather inconspicuous. Small pustules filled
with powdery spores (not waxy like orange rust spores) are formed on
the undersides of infected leaves (Figure 46). These spore masses may
also occur on leaf petioles, canes, and even on the fruit. Infected
fruit are worthless; thus, yield of marketable fruit is reduced (Figure
47). Badly infected leaves may drop prematurely, and in years when the
disease is severe, canes may be defoliated by September.
Figure 45: Symptoms of late leaf rust on the upper
surface of red raspberry leaves. Note the chlorotic spots.
Figure 46: Symptoms of late leaf rust on the lower
surface of red raspberry leaves. Note the masses of powdery yellow
Figure 47: Late leaf rust symptoms on red raspberry
fruit. Note the pustules on individual drupelets.
Unlike the orange rust fungus, the late leaf rust fungus is not
systemic. The rust fungus produces two types of spores (urediniospores
and teliospores) only on raspberries (Figure 48). The alternate host
for the rust is white spruce (Picea canadensis), on which another type
of spore (aeciospore) is produced. The rust apparently does not need
the aeciospores stage to survive on raspberries, because the disease is
found year after year in regions remote from any spruce trees. The
fungus probably overwinters on raspberry canes and, in the following
season, produces urediniospores that serve as the source of primary
inoculum for new infections.
Figure 48: Late leaf rust disease cycle. Taken from the
Compendium of Raspberry Diseases and Insects of the American.
Phytopathological Society. Used with Permission.
The small, numerous, light-yellow spots seen on the
undersurfaces of the leaves are the uredinial pustules that contain the
urediniospores of the fungus. These spores are capable of causing new
infections throughout the growing season. Black, one-celled teliospores
may be found later in the season intermingled with the uredinial
pustules. They are capable of infecting the alternate host (spruce)
through the production of yet another type of spore (basidiospore), but
probably play little part in the life cycle of the rust on Rubus.
Bramble Fruit Rots
Figure 49: Botrytis fruit rot (gray mold) on raspberry
The gray mold fungus is capable of infecting a great
number of different plants. It overwinters as minute, black fungus
bodies (sclerotia) on infected plant debris including dead raspberry
leaves and canes. In early spring, these fungal bodies produce large
numbers of microscopic spores (conidia). Spores are spread by wind
where they are deposited on blossoms and fruits. They germinate when
moisture is present and infection occurs within a few hours. The fungus
usually enters the fruit through flower parts, where it remains
inactive (latent) within the tissues of infected green fruits. As the
fruit matures, the fungus becomes active and rots the fruit. Thus,
while infection actually occurs during bloom, symptoms are usually not
observed until harvest. This is important to remember when one
considers control. Temperatures between 70 and 80°F and moisture on
the foliage from rain, dew, fog, or irrigation create ideal conditions
for disease development. The disease can develop at lower temperatures
if foliage remains wet for long periods.
Vast numbers of conidia are produced on the surface of
infected plant parts, especially fruit. One infected fruit may be
covered by millions of spores, which are carried by wind to cause
additional infections on flowers and ripe fruit.
Bramble Root Diseases
Phytophthora root rot is caused by several related
species of soilborne fungi belonging to the genus Phytophthora. To
date, P. megasperma, P. cryptogea, P. citriocola, P. cactorum,
and at least two additional unidentified Phytophthora species have been
implicated in this disease. The disease occurs on red, black, and
purple raspberries, although in the northeastern United States it has
been documented most commonly on red raspberries. The disease has
reported to occur in blackberries in Kentucky. Phytophthora root rot
can be an extremely destructive disease on susceptible cultivars where
conditions favor its development. Infected plants become weak and
stunted and are particularly susceptible to winter injury; seriously
infected plants commonly collapse and die. Key methods of control
include site selection or improvement to avoid saturated soils and the
selection of more resistant red raspberry varieties.
The disease is most commonly associated with heavy soils or portions of
the planting that are the slowest to drain (lower ends of rows, dips in
the field, etc.). In fact, most declining plants that are considered
suffering from "Wet feet" probably are suffering from Phytophthora root
rot. Symptoms include a general lack of vigor and a sparse plant stand.
Apparently healthy canes may suddenly decline and collapse during the
late spring or summer (Figure 50). In such cases, leaves may initially
take on a yellow, red, or orange color or appear scorched along the
edges. As the disease progresses, affected canes wilt and die. Infected
plants frequently occur in patches, which may spread along the row if
conditions remain favorable for disease development.
Figure 50: Above ground symptoms of Phytophthora root
rot on primocanes of 'Heritage' red raspberry.
Because wilting and collapsing may be caused by other
factors (winter injury, cane borers, etc.), it is necessary to examine
the root system of infected plants to diagnose the disease. Suspect
plants should be dug up and the epidermis (outer surface) scraped off
the main roots and crown. On healthy plants, the tissue just beneath
the epidermis should be white; on plants with Phytophthora root rot,
this tissue will be a characteristic brick red (eventually turning dark
brown as the tissue decays) (Figure 51). Sometimes a distinct line can
be seen between infected and healthy tissue, especially on the
below-ground portion of the crown.
Figure 51: Below ground symptoms of Phytophthora root
and crown rot on red raspberry. Note the sharp line of demarcation
between healthy, white tissue and infected reddish-brown tissue. This
reddish-brown or brick-red discoloration on roots is typical of
Phytophthora root rot.
The fungi persist primarily as mycelium in infected
roots or as dormant resting spores in the soil. When the soil is moist,
reproductive structures (sporangia) are formed upon the infected tissue
or by germinating resting spores (oospores) in the soil. Within each of
these structures a number of individual spores called zoospores are
formed. These zoospores are expelled into the soil during periods when
the soil is saturated with water. The zoospores have 'Tails'
(flagella), which allow them to swim through the water-filled soil
pores to reach new plant parts. Upon reaching a plant root or crown,
the zoospores become attached and infect. As water remains standing and
oxygen is depleted from the root zone, the plant is progressively less
capable of resisting the fungus and infection becomes more likely and
severe. Each new infection site is a potential source of additional
resting spores and zoospores, allowing for epidemic disease development
in sites which are subjected to repeated periods of standing water.
Although the optimum season for infection is not known for certain, it
is likely that spring and fall are particularly favorable periods.
However, it is assumed that infection can occur throughout the growing
season if soil moisture conditions are favorable.
Verticillium wilt is caused by the soilborne fungus Verticillium dahliae and is one of
the most serious diseases of raspberries. This disease reduces
raspberry yields by wilting, stunting, and eventually killing the
fruiting cane or the entire plant. The disease is usually more severe
in black and purple than in red raspberries. Blackberries are also
susceptible to the disease, but seldom suffer severe losses.
Verticillium wilt is usually a cool-weather disease and
is most severe in poorly drained soils and following cold, wet springs.
The appearance of symptoms on new canes frequently coincides with
drought stress during hot, dry, midsummer weather. Key methods for
control are site selection and proper crop rotation to avoid planting
in infested soils.
Symptoms usually appear on black raspberries in June to
early July, and on red raspberries about a month later. The lower
leaves of diseased plants may at first appear to have a dull green cast
as compared to the bright green of normal leaves. Starting at the base
of the cane and progressing upward, leaves wilt, turn yellow, and drop.
Eventually, the cane may be completely defoliated except for a few
leaves at the top (Figure 52). Black raspberry and blackberry canes may
exhibit a blue or purple streak from the soil line extending up the
cane to varying heights (Figure 53). This streak is often not present
or is difficult to detect on red raspberries. In the spring following
infection, many of the diseased canes are dead. Others are poorly
developed and have shriveled buds. The new leaves are usually yellow
and stunted. Infected canes may die before fruit matures, resulting in
withered, small, and tasteless berries.
Figure 52: Verticillium wilt symptoms on black raspberry
Figure 53: Blueish streaks can often be observed on
black raspberry canes affected by verticillium wilt.
Verticillium is a common soilborne fungus. It causes
disease on more than 160 different kinds of plants, including
strawberries, eggplant, tomatoes, potatoes, stone fruits and peppers.
The fungus overwinters in the soil and plant debris as dormant mycelium
or tiny black specks called microsclerotia. The fungus can survive in
the soil for many years. When conditions are favorable, microsclerotia
germinate and produce threadlike fungal filaments (hyphae). These
hyphae can penetrate the root directly, but invasion is aided by breaks
or wounds in the roots. Once inside the root, the fungus grows into the
water-conducting tissue (xylem). The destruction of water-conducting
tissue prevents the movement of water from the roots to the rest of the
plant. Thus, the plant eventually wilts and dies.
Crown Gall and Cane Gall
Crown gall is caused by the bacterium Agrobacterium
tumefaciens. Cane gall is caused by a very similar bacterium,
Agrobacterium rubi. Crown gall is a widespread disease of all brambles.
Cane gall affects black and purple raspberries more frequently than red
raspberries or blackberries. These diseases are particularly serious in
nursery fields where freedom from the disease is essential. The
bacteria induce galls or tumors on the roots, crowns, or canes of
infected plants. Galls interfere with water and nutrient flow in the
plants. Seriously infected plants may become weakened, stunted, and
unproductive. Key methods of control include starting the planting with
disease free plants and crop rotation. A biocontrol agent (Galltrol) is
currently available as a preplant treatment.
Young galls (tumorlike swellings) are rough, spongy, and
wart-like (Figure 54). Galls can be formed each season and vary in size
from a pinhead to several inches in diameter. They develop near the
soil line or underground in the spring. Cane galls occur almost
exclusively on fruiting canes and usually appear in late spring or
early summer. Both crown and cane galls become hard, brown to black,
woody knots as they age. Some disintegrate with time and others may
remain for the life of the plant. The tops of infected plants may show
no symptoms, but plants with numerous galls may be stunted; produce
dry, poorly-developed berries; break easily and fall over; or show
various deficiency symptoms due to impaired uptake and transport of
nutrients and water.
Figure 54: Gall on the root of a crown gall infected red
Crown gall bacteria enter the plant only through natural
openings or wounds in the epidermis or bark of the plant. The bacteria
survive in infested soil for years and can invade the roots and crowns
of susceptible plants through natural growth cracks, tissue damaged by
winter injury, or damage caused by soil insects. Man-made wounds that
occur during pruning and cultivation are important points of entry.
After the bacteria enter plant tissues, an incubation period of 11 to
28 days, or more if the host is dormant, may be required before the
bacteria induce cell proliferation, enlargement, and disorganized
growth, resulting in the production of galls. Bacteria, abundant in the
outer portions of galls, are continually sloughed off into the soil.
The bacteria overwinter in soil and in diseased galls. The following
spring, these bacteria are spread by splashing rain, water, cultivation
(any practice that moves soil), pruning tools and insect feeding. When
they contact wounded tissue of a susceptible host, they enter and
induce gall formation, completing the disease cycle.
Virus Diseases of
Red and black raspberries are susceptible to numerous
viruses. Raspberries probably suffer greater infection and more serious
damage from viruses than any other fruit crop in the United States.
Virus infection in raspberries can reduce fruit yields 70 percent or
more. There are four main virus-induced diseases of raspberries:
mosaic, leaf curl, streak, and tomato ringspot. Key control methods
include starting the planting with disease free (virus indexed) plants
and eradication of wild hosts as well as infected plants within the
Other disorders of raspberries can cause symptoms
similar to viruses. Late-spring frosts, mineral deficiencies (such as
iron and nitrogen), powdery mildew, pesticide injury, and feeding by
leafhoppers, aphids and mites can all cause symptoms similar to those
caused by various viruses. Positive identification of a bramble virus
or virus complex cannot be based on foliar symptoms alone. Greenhouse
and laboratory tests using specific scientific techniques are required
for positive identification of viruses.
This disease is caused by a virus complex (more than one
virus involved). Viruses of the mosaic complex (Rubus yellow net, black
raspberry necrosis, raspberry leaf mottle and raspberry leaf spot
virus) cause the greatest reduction in growth, vigor, fruit yield, and
quality of any of the bramble viruses. No raspberry plants are immune,
but black and purple cultivars are damaged more severely than red
cultivars. The symptoms of mosaic vary considerably, depending upon the
cultivar grown, which virus or viruses of the complex are involved, and
time of year. Symptoms are most evident on new canes during cooler
weather of spring and fall. Symptoms may disappear in the summer when
temperatures are high. This is an important point to remember when
considering control of virus diseases. Even though symptoms may
disappear temporarily, plants remain infected for life. Infected canes
are usually short and less vigorous than healthy canes. Leaves are
mottled with yellowish or light green spots on a darker green
background (Figure 55). On more susceptible cultivars, leaves become
puckered with large, dark-green blisters surrounded by yellowish or
yellowish-green tissue. Leaves that develop in hot weather may be
symptomless or show only faint mosaic pattern with yellow flecks in the
normal green color. Leaves formed in late summer show a fine,
yellowish, speckled mottling.
Figure 55: Mosaic virus symptoms on raspberry leaves.
Note the mottled areas of dark green and light green or yellow.
Mosaic-infected plants are often progressively more
stunted each year. In addition to leaf symptoms, the fruit yield is
reduced and may be dry, seedy (often crumbly), and lack flavor. On
black and purple raspberries, the tops of newly-infected canes often
curl downward, turn black, and die.
The raspberry mosaic virus complex is spread almost
exclusively by one species of insect, the large raspberry aphid
(Amophorophora agathonica). The aphid is widespread and feeds on the
undersides of leaves near the tip of the canes. The aphids become
contaminated with the viruses and can spread the viruses to healthy
plants up to a quarter of a mile or more away. The mosaic virus can
also be spread by commercial propagation from infected plants and
movement of the diseased nursery plants.
Leaf curl is less common than the mosaic complex, but it
is considerably more destructive. Infected plants are worthless and
should be destroyed immediately. The yield of infected raspberries can
be reduced up to 70 percent. Infected black raspberry plants may
degenerate and die after two or three years.
Leaf curl symptoms are easily recognized. Leaves on
infected plants are uniformly small, dark green, crinkled, and tightly
curled downward and inward. When diseased shoots first appear, they are
pale yellowish-green, but they soon turn dark green, become stiff and
brittle, and usually do not branch. Each year the plant loses more
vigor and is progressively more dwarfed. Fruiting laterals are shorter
and more upright than normal ones. Berries on infected plants may ripen
prematurely and are small, dry, seedy, and crumbly.
The raspberry leaf curl virus, the causal agent of
raspberry leaf curl disease, is spread exclusively by the small
raspberry aphid (Aphis rubicola). Heavy populations of this aphid can
cause severe inrolling of leaves even in the absence of the leaf curl
virus. Winged forms of the aphid can transmit the virus to healthy
raspberries from nearby infected brambles. Windborne aphids may spread
the disease several miles.
Raspberry streak, caused by tobacco streak virus, is
generally a minor, but widespread disease. It is presently limited to
northern Ohio, western Pennsylvania, and western New York. Streak
affects only black raspberries.
The most obvious symptom of the disease is numerous
purplish streaks that appear on the lower parts of infected canes.
Usually, the streaks are less than an inch long. Terminal leaves on
infected canes are often hooked or recurved, twisted or rolled, and
darker green than normal. Leaves on the lower positions of the cane may
show yellowing along veins and mottling. Fruits on infected canes are
smaller than normal, dull, seedy, and crumbly and lack flavor. The
individual drupelets often ripen unevenly, giving the fruit a blotched
This virus disease occurs only in red raspberries and is
widespread in the major red raspberry-producing areas of the Pacific
Coast and northeastern United States. Infected plants may appear
normal, but they are usually somewhat less vigorous than healthy
plants. The most obvious symptom of the disease is the production of
small, crumbly berries that fall apart when touched. The crumbly berry
is caused by the failure of some of the tiny fruitlets (druplets),
which make up the fruit, to develop.
The tomato ringspot virus can affect many other species
of woody and herbaceous plants. This virus is transmitted through the
soil by the dagger nematode (Xiphinema americanum).
of Virus Diseases
Always start new plantings with the highest-quality
plants available. Use only certified, disease-free, virus-indexed
stock. Avoid obtaining uninspected plants from friends or neighbors.
Select a planting site that is sunny and fertile and has good air and
water drainage. Destroy all wild and neglected raspberries and other
brambles located within 500 to 1,000 feet of your planting site.
Do not plant black or purple raspberries near red
raspberries, even though the red raspberries appear to be healthy. Red
raspberries may have latent infections. This means that they can be
infected, but do not show symptoms. Even though infected plants are
symptomless, the virus can still be transmitted from them to healthy
plants. If black and red raspberries are planted together, separate
them as far apart as possible. If possible, plant black raspberries
upwind from reds. The reason for this is the aphids that transmit
viruses are generally blown or carried by wind rather than by active
flight. Therefore, you do not want aphids to be blown from your red
raspberries to your more susceptible black raspberries.
Go through the raspberry planting at least twice a year
and remove all plants showing any virus symptoms. This should be done
once about mid-June and again in August or September. Before removing
infected plants, kill all aphids on them by spraying infected plants
with an insecticide a day or two before removal. Dig out the diseased
plants, including roots, and dispose of them away from the planting
site. In established plantings, where more than 5 to 10 percent of the
plants show visible virus symptoms, removal of infected plants probably
will not pay. In this case, maintain the planting until fruit yield
becomes unprofitable, then destroy it. It is unwise to establish new
plantings next to old, infected ones. Maintain strict aphid control at
all times, especially in late spring and early summer when aphid
populations are highest.
If the virus is transmitted by nematodes, the nematodes
must be controlled in order to control the disease. Have the soil
tested for plant parasitic nematodes before planting. Samples should be
taken in July of the year preceding planting. Spring samples, taken
when soils are cold, are not accurate and do not give the grower
sufficient time to apply a preplant nematicide. Information on
collecting soil samples and submitting them for analysis is available
from your Extension service.
In an organic disease management program where emphasis
is placed on reducing overall fungicide use, it is essential to
identify any available disease resistance and use it. Unfortunately,
resistance to most of the major diseases is not available in most
commercially grown raspberry and blackberry cultivars in the Midwest.
Thus, the disease management program must rely mainly on the use of
cultural practices and efficient fungicide use. Whereas resistant
cultivars are not generally available for most diseases, cultivars do
vary greatly in their level of susceptibility to certain diseases. If
resistance is not available, those cultivars that are highly
susceptible to important diseases should at least be avoided.
Phytophthora Root Rot
Phytophthora root rot is most serious on red raspberries
and some of the hybrids. The black raspberry varieties 'Cumberland' and
'Munger' are reported to be susceptible. The cultivars 'Bristol',
'Dundee' and 'Jewel' appear to be moderately to highly resistant. Among
red raspberry cultivars, none are immune to the disease, but cultivars
do differ greatly in their level of susceptibility. Among varieties
grown in the Midwest and Northeast, 'Titan' and 'Hilton' are extremely
susceptible, with 'Festival', 'Heritage', 'Reveille', and 'Taylor'
moderately to highly susceptible. 'Newburgh' is somewhat resistant, and
'Ratham', 'Boyne', 'Killarney', and 'Nordic' are considered to be
Red raspberries are more tolerant than black
raspberries. 'Cuthbert' and 'Syracuse' appear to be resistant under
field conditions. Black raspberries are highly susceptible.
Blackberries are susceptible, but the disease is seldom a serious
Red raspberries are immune. Other brambles are
susceptible. Of blackberries, 'Eldorado', 'Raven', 'Snyder', and 'Ebony
King' are reported to be resistant. The Arkansas erect types (Arkansas
Indian series) are reported to be resistant to orange rust.
Blackberries are resistant. Black and purple raspberries
are more severely affected than red raspberries. Of the purple or black
raspberries, 'New Logan',・'Bristol',・and 'Black Hawk' are tolerant and
'Cumberland' is susceptible. The red raspberries 'Milton', 'September',
'Canby', and 'Indian Summer' are resistant because the aphid vectors of
the virus avoid them.
Leaf Curl Virus
Blackberries are symptomless. All raspberries are
Tomato Ringspot Virus
Red raspberries and blackberries are susceptible.
Black and purple raspberries are susceptible.
Cultural Practices for
Disease Control in Brambles
The use of any practice that reduces or eliminates
pathogen populations or creates an environment within the planting that
is less conducive to disease development must be used. Cultural
practices are the major means of control for several important bramble
diseases. The following practices should be carefully considered and
implemented whenever possible in the disease management program.
Use Virus-Indexed Planting Stock
Always start the planting with "Healthy" virus-indexed
nursery stock from a reputable nursery. The importance of establishing
plantings with virus-indexed nursery stock cannot be overemphasized,
since the selection of planting stock and planting site are the only
actions a grower can take to prevent or delay the introduction of most
virus diseases. Plants obtained from an unknown source or neighbor may
be contaminated with a number of pathogens that experienced nurserymen
work hard to control.
Proper site selection is critical to developing a
successful disease management program. Establishing a planting on a
site that is conducive to disease development is a critical error. Such
plantings may be doomed to failure, regardless of the amount of
pesticide a grower uses. The following considerations should play a
major role in the disease management program.
Soil drainage - Soil drainage (both
surface and internal drainage) is an extremely important
consideration when selecting a planting site. Planting brambles on
poorly or even marginally drained sites is a poor management decision.
For example, poorly drained soils that are frequently saturated with
water are highly conducive to the development of Phytophthora root rot,
especially in red raspberries. Even in the
absence of plant disease, wet soils are not conducive to good plant
growth and productivity.
Any practice such as tiling, ditching, or planting on
ridges that aids in removing excessive water from the root zone will
increase the efficacy of the disease management program. Once the
planting is established, it is difficult, if not impossible to improve
Site Exposure (Air Circulation and Sunlight
Exposure) - Avoid sites that do not have full exposure to
sunlight, such as shaded areas near woods or buildings. In addition,
sites with poor air circulation that tend to accumulate still, damp air
should be avoided. Planting rows in the direction of the prevailing
winds will help promote good air circulation and rapid plant drying.
The primary reason for the above considerations is to promote
faster drying of canes, foliage, and fruit. Most plant
pathogenic fungi and bacteria require water on plant surfaces in order
to penetrate and infect the plant. Any practice that reduces wetness
duration (speeds drying time) of susceptible plant parts is beneficial
to the disease management program.
Previous Cropping History - Avoid
establishing plantings on sites that have a previous history of
problems with Verticillium wilt, either in previous plantings of
brambles or other susceptible crops. In general, it is not a good
practice to plant brambles immediately after solanaceous or other
Verticillium-susceptible crops, such as tomatoes, potatoes, peppers,
eggplant, melons, strawberries and other related crops. Certain common
weeds, such as black nightshade, redroot pigweed, lamb's-quarters, and
horsenettle will also support growth of the Verticillium fungus, and
fields with a high population of these weeds should also be avoided.
This is particularly important if Verticillium wilt is known to have
been a problem on the site in the past. The fungus that causes
Verticillium wilt can survive in soil for very long periods of time (at
least 14 years in California). If a site is known to have had a problem
with Verticillium wilt within the last 5 to 10 years it should probably
not be used for establishing plantings of Verticillium-susceptible
bramble cultivars unless the soil is fumigated before planting.
Most brambles are susceptible to Verticillium wilt and
when the disease becomes established within the planting, it can be
devastating. Resistance to Verticillium wilt in the cultivars currently
grown in the Midwest is not available. In general, black raspberries
are significantly more susceptible than red raspberries, and (in
general) blackberries are the least susceptible.
If the site has a previous history of Phytophthora root
rot, either in previous bramble plantings or other perennial fruit
crops, it should probably be avoided. Phytophthora spp. (like
Verticillium) can also survive in soil for extended periods of time. It
is important to remember that Phytophthora root rot is usually
associated with poorly drained (wet) sites and improving soil drainage
is one of the principal means of control.
If nematodes have been a problem in previous crops or
they are suspected to be a problem on the site, a soil analysis to
determine the presence of harmful nematodes should be conducted.
Nematodes are most likely to be a problem on the lighter (sandy) soils.
Nematode sampling kits and instructions on taking samples can be
obtained through your Extension office. Infested sites may be treated
with an approved nematicide before planting if sampling indicates a
need to do so.
Proximity (closeness) to established bramble
plantings and wild bramble plants - Ideally, a new planting
should be isolated as far as possible from old established plantings or
wild bramble plants that serve as reservoirs for diseases and other
pests. The benefits of using virus-indexed plants to establish a new
field are greatly reduced if the fence row around the planting or a
woods directly adjacent to the planting contains wild, virus-infected
or orange rust-infected plants. The same is true if a new planting is
established next to an old planting that has disease problems.
Currently no information is available on exactly how far
away from an established planting or weeded area is "Far enough". The
distance of 600 to 1000 feet is used commonly in Extension literature;
similarly, the New York State virus certification program requires that
nurseries in the program use a minimum distance of 1,000 ft. It is
probably safe to say "The farther the better".
Crop Rotation (Replanting Brambles)
When replanting brambles on the same site, the practice
of crop rotation must be considered. Due to the build up and
persistence of soilborne plant pathogens, replanting brambles on the
same site is not recommended without the use of crop rotation. Soil
fumigation is not an option in organic production systems.
At present, data describing how long a rotation is
required before replanting brambles on the same site is not available.
In fact, this requirement is probably different for every different
planting site. Once again, the safest recommendation is probably "the
longer, the better", particularly if the site has a history of
All soilborne diseases, however, are not the same. For
instance, Verticillium wilt generally becomes a problem only after
populations of the Verticillium fungus slowly build up to high levels.
Thus, if no brambles or other susceptible crops are grown for a
suitable period (probably at least 5 years), the fungus population
declines and brambles can be reintroduced and grown for a number of
years before the population builds back up to damaging levels. This
same principle is true for many harmful nematodes, but it is not true
for Phytophthora root rot. The Phytophthora fungi reproduce very
rapidly under proper environmental conditions, so even a low population
can rebuild to damaging levels within one or two seasons.
Crop rotation will not eliminate all problems associated
with soilborne diseases. It should always be integrated with other
control measures, such as the choice of resistant or
partially-resistant cultivars, improvements in drainage, etc. Where
other control measures cannot be used (for instance, the site cannot be
adequately drained), it is not advisable to replant brambles.
Avoid Excessive Fertilization
Fertility should be based on soil and foliar analysis.
The use of excessive fertilizer, especially nitrogen, should be
avoided. Sufficient fertility is essential for producing a crop, but
excessive nitrogen can result in dense foliage that increases drying
time in the plant canopy, i.e., it stays wet longer. Research has shown
that excessive use of nitrogen can result in increased levels of
Botrytis fruit rot (gray mold).
Control Weeds In and Around the Planting
Good weed control within and between the rows is
essential. From a disease-control standpoint, weeds in the planting
prevent air circulation and result in fruit and foliage staying wet for
longer periods. For this reason, most diseases caused by fungi are
generally more serious in plantings with poor weed control than in
those with good weed control. Furthermore, some disease-causing
organisms (Verticillium wilt fungus, crumbly berry virus) can build up
on certain broadleaf weeds in the planting. Any practice that opens up
the canopy in order to increase air circulation and reduce drying time
of fruit, foliage and young canes is generally beneficial to disease
control. Controlling wild brambles (which are weeds) near the planting
is also important because they can serve as a reservoir for several
important diseases and insect pests.
Sanitation (Removal of Overwintering Inoculum)
The fungi that cause anthracnose, cane blight, spur
blight, Botrytis fruit rot, cane and leaf rust and several other
important diseases overwinter within the planting on canes infected
during the previous year. Pruning out all old fruited canes and
any diseased new canes (primocanes) immediately after harvest and
removing them from the planting breaks the disease cycle and greatly
reduces the inoculum. All infected pruning waste should be removed from
the field and destroyed. If you are attempting to minimize fungicide
use, good sanitation (removing old fruited canes) is critical. If old
fruited canes cannot be removed before winter, they should definitely
be removed before new growth starts in the spring.
For fall bearing raspberries, such as Heritage, all
canes are cut off each year. Removing all cut canes from the planting
will aid the disease management program. If it is impossible to remove
pruned canes from the field, they should be chopped in place as quickly
as possible with a flail mower to speed decomposition before new canes
Plant population and canopy management
Any practice that alters the density of the plant canopy
and increases air circulation and exposure to sunlight is generally
beneficial to disease control. Optimizing between-row and within-row
spacings and maintaining interplant spacings through judicious cane
thinning throughout the life of the planting is desirable. Ideally,
rows for red raspberries should not be over 2 feet wide and should
contain about 3 or 4 canes per square foot. Control of plant vigor,
particularly through avoidance of high levels of nitrogen and careful
use of cane vigor control techniques, can greatly aid in improving the
canopy density. Specialized trellis designs for various Rubus spp. can
further improve air circulation and increase exposure to sunlight, as
well as increase harvest efficiency. Trickle irrigation, as opposed to
overhead sprinkler irrigation, greatly reduces the wetting of foliage
and fruit and the risk of splash dispersal of several important fungal
Removing young fruiting shoots (before they exceed 4
inches in length) from the lower portions of canes (approximately the
lower 20 inches) will remove fruit that might become soiled. This
practice also removes shoots that disproportionately contribute to
shading and poor air circulation in the canopy.
For information on methods for cane vigor control,
trellis designs and optimum spacing requirements, the following book is
very useful: Bramble Production Guide, edited by Marvin Pritts and
David Handley. It can be purchased from: Northeast Regional
Agricultural Engineering Service, 152 Riley-Robb Hall, Cooperative
Extension, Ithaca, NY 14853. Phone: 607-255-7654.
Inspect the Planting Frequently and Rogue Out
(Remove) Diseased Plants
Plants showing symptoms of virus diseases, rosette, or
orange rust must be removed and destroyed immediately, including the
roots, whenever they are found. These plants may bear fruit, but it
will be of poor quality. The longer these plants remain, the greater
the chances that other plants will become infected. Viruses and the
orange rust fungus are systemic and can move to adjacent plants via
root grafts. Because of this possibility, use a flag to mark the
locations where diseased plants are removed so the adjacent plants can
be checked frequently for new symptoms.
For orange rust, it is particularly important to
inspect the planting early in the growing season. The planting should
also be inspected on a routine basis (at least once a week) from the
time growth starts in the spring through harvest. New leaves of early
spring growth on orange rust infected plants are chlorotic (yellowish),
shoots are bunched and spindly. They are easy to identify in the
spring. It is important that infected plants be identified and removed
prior to the development of the "Orange rust" pustules on the leaves.
If these pustules are allowed to develop, they will produce large
numbers of aeciospores which will spread the disease. If infected
plants are not removed early in the spring, they become more difficult
to identify later in the growing season.
Early spring is also a good time to inspect for virus
diseases. Symptom expression of many viruses is more obvious during
cool growing conditions. The higher temperatures of mid-to late summer
often reduce virus symptoms making infected plants difficult, if not
impossible, to detect.
Adjust Production Practices to Prevent Plant Injury
Many plant pathogens take advantage of wounds in order
to penetrate and infect the plant. Therefore, any practice that
minimizes unnecessary physical damage to the plant is beneficial to the
disease management program. Cane blight and bacterial crown gall are
two important pathogens of brambles that enter the plant almost
exclusively through wounds. The use of sharp pruning tools will help
minimize damage to canes during pruning operations. Prune only when
necessary (avoid cosmetic pruning of primocanes) and avoid pruning
during periods when plants are wet or immediately before wet weather is
forecast. Most plant pathogens require water on the surface of plant
tissues before they can penetrate the plant. Providing proper cane
support through trellising or otherwise tying the canes will aid
greatly in avoiding abrasions from sharp spines and wind whipping of
plants during windy conditions. Proper spacing between rows and the use
of the proper size equipment will also prevent plant damage.
Proper Harvest, Handling and
Storage of Fruit
Proper harvesting and storage methods are critical
components of the disease management program. It is of little value to
produce high-quality fruit in the field if it is bruised or crushed
during harvest or permitted to rot during storage. Raspberry and
blackberry fruit are very perishable. Even under the
"Best conditions" these tender fruits are extremely susceptible to
physical damage and post harvest rots. The following practices need to
be considered well in advance of initiating the harvest. The proper
implementation of these practices will aid greatly in providing your
customers with the best quality fruit possible.
a) Handle all
fruit carefully throughout all phases of
harvest, transport and sale. Bruised or crushed (leaky) fruit are much
more susceptible to fungal infection and rot than firm, intact fruit.
b) Harvest all
fruits as soon as they are ripe. During
periods of warm weather, harvest may require picking intervals as short
as 36 to 48 hours. Pick early in the day before the heat of the
afternoon. Overripe fruit in the planting will attract a number of
insect pests and provide a source for inoculum buildup of fruit rotting
c) It is highly
desirable to combine harvesting and
packing into one operation. This prevents unnecessary handling and
additional physical injuries.
d) If possible,
train pickers to remove damaged or
diseased berries from the field. Some growers have programs where they
pay the picker as much, or more, for damaged berries picked into
separate containers, than for healthy berries. This is a good
sanitation practice that reduces inoculum levels of fruit rotting-fungi
in the field. Providing hand-washing facilities in the field so pickers
can periodically clean their hands, should be helpful in reducing the
movement of fungus spores that are encountered by touching rotten
e) Pick into
shallow containers. Ideally, fruit should
be no more than 3 to 4 berries deep; this greatly reduces bruising and
crushing the fruit, which results in juice leakage that encourages the
development of fungal fruit rots.
fruit immediately after harvest. Fruit
should be cooled as close to 32°F as possible within a few hours
after harvest. This temperature should be maintained throughout storage
and, if possible, throughout shipment and sale. If you do not have
refrigeration, fruit should be placed in the coolest place possible.
Never allow the fruit to sit in the sun.
condensation of water on fruit after it is
removed from cold storage. This is best accomplished by enclosing it in
a waterproof over-wrap before it leaves the refrigerated area. The
over-wrap should be kept in place until the fruit temperature has risen
past the dew point.
h) Sell the
fruit immediately ("Move it or lose it".
Many berries produced in the Midwest are sold to pick-your-own
customers or directly at farm markets, and are not refrigerated prior
to sale. Customers should be encouraged ("educated" to handle,
refrigerate, and consume or process the fruit immediately in order to
assure the highest quality possible. We must remember that even under
the best conditions, raspberry and blackberry fruits are very
Bramble disease control
ft from wild brambles
tolerance or resistance
drying (weeds, pruning)
3 days before rain
of diseased pruned canes
Key: ++= most important
controls; += helpful controls; -= no effect.
a Viruses: Mosaic (rasp.), Leaf Curl
(raspberry, with blackberry symptomless), Ringspot (red raspberry), and
Streak (purple and black raspberry).
b Cane blights: anthracnose, cane blight, spur
blight, and Botrytis blight.
c Rotation effective for ringspot virus only;
2 years of grass crop (e.g. corn) with excellent weed control before
planting red raspberry should eliminate need to fumigate for Xiphinema,
a nematode vector.
d Rotation for Verticillium wilt:
Avoid fields planted to susceptible crops (tomatoes, potatoes,
eggplant, peppers, strawberries, raspberries, stone fruit) within the
past 5 years. Avoid fields with history of Verticillium wilt unless
soil is fumigated.
e Virus resistance, tolerance, and immunity:
Mosaic-Blackberries are not affected; black and purple raspberries are
more severely affected than red raspberries. Of purple and black
raspberries, "New Logan", "Bristol", and "Black Hawk" are tolerant;
"Cumberland" is susceptible. Of red raspberries, "Milton", "September",
"Canby", and "Indian Summer" are Resistant because aphid vectors avoid
them. Leaf Curl-Blackberries are symptomless; all raspberries are
affected. Tomato Ringspot-Red raspberries are affected. Streak - Black
and purple raspberries are affected.
f Verticillium tolerance: Most blackberries
are resistant; red raspberries are more tolerant than black
raspberries. "Cuthbert" and "Syracuse" red raspberries appear to be
resistant under field conditions.
g Orange Rust resistance: Red raspberries are
immune. Other brambles are affected. Of blackberries, "Eldorado",
"Raven", "Snyder", "Ebony King", "Choctaw", "Commanche", "Cherokee",
and "Cheyenne" are reported resistant.
h Fungicide program for cane blights: The
lime-sulfur spray (delayed dormant) is most important for anthracnose
and cane blight.
i Fungicide program for powdery mildew: Sulfur
will provide good control of powdery mildew.
j Keep blacks and purples away from reds
because mosaic virus can spread from reds and is more severe on blacks
and purples; Keep all reds away from blackberries because blackberries
can be a symptomless carrier of leaf curl
Fungicide use strategies for
Unfortunately, there are
not many options to choose from when one considers current fungicide
use strategies. The current options are:
1. Do Not Use Fungicides
This is always an option, but may not be a wise
decision for commercial grape plantings in the Midwest. This option
should not be confused with “organic” production. Grape growers in
“organic” production systems will most probably use Sulfur or Copper to
some extent for disease control. Sulfur and Copper are fungicides.
Growers that choose not to use fungicides must rely completely on
cultural practices, disease resistance, or biological control agents or
products for disease control. For strawberries, caneberries and
blueberries organic fungicides are often of little value against the
more common diseases such as Botrytis fruit rot (gray mold); therefore,
little or no fungicide will probably be used in organic production of
2. Protectant Fungicide Program
In a protectant program, fungicides are used as a
protective barrier on the plant surface. This chemical barrier prevents
the fungus from entering the plant. It works much like paint on a piece
of wood to keep out water. Protectant fungicides (such as sulfur and
copper) are not systemic and cannot move into plant tissues. Once the
fungus penetrates into the plant, protectant fungicides will not
control it. As the protective barrier breaks down or new foliage is
produced, additional applications are required to maintain the
Protectant fungicide programs have been, and still are
very effective; however, they generally result in a fairly intensive
use of fungicide. On grapes, protectant fungicides are usually applied
on a 7-10 day schedule early in the growing season and on a 10-14 day
schedule later in the season. Obviously, maintaining a protective
barrier on the plant surface throughout the growing season requires
The following is a brief description of some disease
control materials that are commonly or traditionally used in organic
production systems. Copper fungicides, elemental sulfur and liquid lime
sulfur are the old “standard” fungicides, and have been used for many
years in organic production systems.
Note: Prior to using any material in the organic
system, it is important that the grower consult his/her organic
certification agency or program to be positive that use of the material
When different formulations of copper are dissolved in
water, copper ions are released into solution. These copper ions are
toxic to fungi and bacteria because of their ability to destroy
proteins in plant tissues. However, because copper can kill all types
of plant tissues, the use of copper fungicides carries the risk of
injuring foliage and fruit of most crops. Factors promoting this injury
include: 1) the amount of actual copper applied, and 2) cold, wet
weather (slow drying conditions) that apparently increases the
availability of copper ions and, thus, increases the risk of plant
injury. Because of the potential to injure plants and to accumulate in
soil, the use of copper fungicides in conventional production systems
has largely been replaced with conventional fungicides that are
generally safer to plant tissues and often more effective.
Several terms are used when discussing copper as a
fungicide. The original material used was copper sulfate (also known as
blue vitriol or bluestone). When this material was combined with lime
in the French vineyards, the combination became known as Bordeaux
Bordeaux mixture is a mixture of copper sulfate and
hydrated lime in water. It has long residual action and has been used
for years to control many diseases, including downy mildew and powdery
mildew of grape. It can be made (mixed) on site by combining copper
sulfate with spray grade lime. It is also commercially available as a
dry wettable powder.
Fixed Copper Fungicides
Following the discovery and use of Bordeaux mixture,
several relatively insoluble copper compounds or fixed coppers were
developed. Fixed copper formulations release less copper ions and are
generally less injurious to plant tissues (safer to use) than Bordeaux
mixture, but their use is still limited because of their potential to
injure plants and lack of compatibility with other pesticides. Some of
the more common commercial formulations of fixed copper include
C-O-C-S, Kocide 101, Tribasic Copper sulfate, Champ, and Tenn-Copp 5E.
There are several fixed copper fungicides registered for use on small
Sulfur is available as liquid lime sulfur and as dry
wettable powders or liquid (flowable) formulations of elemental sulfur.
Liquid Lime Sulfur
Liquid lime sulfur can be used at high concentrations as
a dormant spray on raspberries and blackberries for control of cane
blight, spur blight and anthracnose and on grapes for control of
anthracnose. At high concentrations, it should be used only when plants
are dormant. It can cause severe damage if applied after green foliage
appears. Lime sulfur has a foul odor that many people dislike. It is
also registered for use on grapes and caneberries as a more dilute
concentration for use during the growing season.
Dry Wettable Sulfurs or Flowable Sulfurs
Sulfur for use as a fungicide is available under many
trade names. The microfine wettable sulfurs or flowable sulfurs are
usually much less injurious to foliage and fruit than liquid lime
sulfur, but their use during hot weather (above 85°F)
may result in some leaf burning and fruit damage. Sulfur fungicides are
very effective for control of powdery mildew on most fruit crops, but
are not highly effective for control of most other fruit crop diseases.
Sulfur is very toxic to foliage of certain grape varieties (mainly
American grapes) including Concord, Chancellor, DeChaunac and Foch.
Sulfur is relatively safe on most other varieties see Table 6, page 68.
Applications after the fruit begins to ripen may pose problems during
fermentation if the grapes are intended for wine making.
Growers should note that sulfur is lethal to some
beneficial insects, spiders and mites. These beneficial insects are
natural predators of harmful insects and mites that affect fruit crops.
Killing these beneficial insects may increase certain pest problems,
Specific comments on fungicide use will be made in the
text for each crop where applicable.
“New Alternative” Disease Control
Materials for Small Fruit
Many products are currently available or currently being
introduced as “biological control agents” or “biopesticides”. These
include living microorganisms, “natural chemicals such as plant
extracts, and “plant activators” that induce resistance in plants to
disease. For most of these products, independent evaluations are
currently being conducted; however, their effectiveness under moderate
to high disease pressure is uncertain. Although many of these new
products have great potential for use within organic production
systems, their effectiveness needs to be determined in field tests. It
is important to remember that registration of these materials for
control of a specific disease on a crop is no guarantee that they will
provide effective control under moderate to heavy disease pressure. In
addition, many products may be effective for only one or a few diseases
and most have very limited residual activity (they have to be applied
often). It is also important to remember that these are registered
pesticides and growers need to be certain that their use is permitted
within their organic certification program.
The biological control committee of the American
Phytopathological Society has developed a web page for “Commercial
Biocontrol Products Available for Use Against Plant Diseases”. The
web page address is: www.oardc.ohio-state.edu/apsbcc/productlist.htm.
This web page lists all the products currently available along with
information such as registered crops and diseases controlled. It also
lists the name of the company that manufacturers or distributes the
product along with phone numbers and web site addresses. This site is
updated regularly and is a valuable resource for growers interested in
The following are a few of the most common “alternative
disease control products currently registered for use on small fruit.
AC10 (Ampelomyces quisqualis) is a
biofungicide registered for control of powdery mildew in grapes,
strawberries, blueberries, raspberries, currants, and gooseberries. A.
quisqualis is a fungus, that parasitizes powdery mildew fungi.
Preliminary results in grapes in Michigan show moderate disease
control. Adding an adjuvant such as Nufilm (0.02% v/v) enhances its
efficacy. Application should start as soon as susceptible tissue
becomes available and continue on a 7 to 14 day schedule. A minimum of
2 sequential applications if needed to maintain the population of A.
quisqualis. The following chemicals cannot be tank-mixed with AQ10:
sulfur and potassium salts of fatty acids.
Armicarb 100 (potassium bicarbonate=baking
powder) is a reduced-risk, protectant (contact) fungicide. Armicarb 100
is registered for control of powdery mildew and other diseases in
grapes, blueberries, strawberries, and brambles. Preliminary results in
grapes in Michigan indicate moderate control of powdery mildew. Start
applications at the first sign of disease and continue on a 7-14 day
schedule. The preharvest interval (PHI) on all crops is 0 days.
Galltrol (Agrobacterium radiobactor strain
84) is a biological control product for control of crown gall, caused
by Agrobacterium tumifaciens on several tree fruit and nut crops. The
active ingredient is the bacterium, Agrobacterium radiobactor strain
84. On small fruits it is effective for control of crown gall on
raspberry and blueberry. It is not effective for controlling crown gall
on grapes. It is purchased as a pure culture grown on agar in petri
plates. The bacterial mass from one plate is diluted into one gallon on
non-chlorinated water and plants are treated with a pre-plant dip in
the solution or as a soil drench.
Kaligreen (potassium bicarbonate = baking
powder) is a reduced-risk protectant (contact) fungicide. Kaligreen is
registered for control of powdery mildew on grapes, strawberry,
brambles (raspberry and blackberry) and blueberry. It provides good
control of powdery mildew when applied on a frequent-protectant program
of 7 to 10-day intervals. It has little or no efficacy against most
other fungal diseases on small fruit. It is formulated as a
micro-encapsulated powder that is mixed in water and sprayed directly
on the crop. Kaligreen has a preharvest interval (PHI) of 1 day on all
small fruit crops.
Messenger (harpin) is a reduced risk product
registered for use on grapes, blueberries, cranberries, strawberries,
brambles, and currants. The active ingredient is derived from a protein
produced by certain bacteria. This protein stimulates natural plant
defenses. Messenger has no direct effect on pathogens. The efficacy of
this material for disease control or suppression has not been
sufficiently confirmed. Messenger has a 0 day PHI.
Mycostop (Streptomyces griseoviridis strain
K61) is a biocontrol product registered for use on all fruit crops for
control of several important pathogenic fungi that cause seed, root,
and stem rot and wilt diseases. The active ingredient is the bacterium,
Streptomyces griseoviridis strain K61. It is sold as a powder
formulation that is mixed with water and applied as a spray or a drench.
Oxidate (hydrogen dioxide) is a
broad-spectrum bactericide/fungicide registered for use in grapes,
blueberries, cranberries, strawberries, and brambles. It is a rather
corrosive material and works by oxidizing fungal and bacterial cells.
The efficacy of the material for disease control has not been
sufficiently confirmed on several diseases. In one Ohio fungicide
evaluation, it provided no control of grape black rot.
Serenade (Bacillus subtilis) is a
biocontrol product registered for control of powdery mildew, Botrytis
bunch rot and sour rot in grapes. Serenade is also reported to provide
some suppression of downy mildew. This product needs further
evaluation, but preliminary results show a moderate level of control of
Botrytis bunch rot and powdery mildew. Serenade did not control grape
black rot in Ohio. Good coverage is important for control. Applications
are recommended on a 7-10 day schedule. Serenade has no maximum
seasonal application rate and has a 0 day PHI.
Trichodex (Trichoderma harzianum) is a
biofungicide registered for use on all small fruit crops for control of
a wide range of diseases, but primarily for control of Botrytis fruit
rot. It is sold as a wettable powder formulation that is mixed with
water and sprayed directly onto the plants.
Trilogy (Clarified Hydrophobic Extract of
Neem Oil). The label states that Trilogy is a broad spectrum fungicide
of certain diseases and controls mites in citrus, deciduous fruits and
nuts, vegetable crop, cereal grains and other miscellaneous crops. The
label does not state what diseases are controlled on specific crops.
Trilogy is registered for use on grapes, strawberry, brambles
(raspberry and blackberry), and blueberry. Trilogy is a liquid that is
applied for diseases as a 1% solution in sufficient water to achieve
complete coverage of the foliage.
As the efficacy of these new materials is tested and
validated, they will be included in these guidelines where appropriate.
Efficacy of Disease
for Powdery Mildew
Powdery mildew is different from most other plant
diseases caused by fungi, because the fungus that causes it lives
almost entirely on the surface of infected plant parts. The fungus may
penetrate only one cell layer deep into the plant. Thus, it is exposed
to eradication following topical treatment with a range of products
that do not affect many other pathogenic fungi that colonize deeper
into infected plant tissues. Research in New York and other locations
has demonstrated that many new and “alternative materials can provide
effective control of powdery mildew if applied often enough (7 day
schedule) through the growing season. These
materials burn out the fungus growing on the surface,
but do not provide protection against new infections; thus, repeated
applications are important. These materials include: Nutrol
(manopotassium phosphate); Kaligreen and Armicarb (potassium
bicarbonate-baking soda); oils such as Stylet Oil and Trilogy; and
dilute solutions of hydrogen peroxide (Oxidate).
Unfortunately, these materials have little or no effect
on many other small fruit diseases. In addition, organic growers need
to consult with their certification agency or program to be sure that
any material they use is “certified” or acceptable as organic.
Bramble Disease Control
sulfur is recommended for use on brambles as a delayed-dormant
early spring (when buds show 1/4 inch green). It is used at the rate of
gal per acre. If applied at this rate
later in the season (after ¼ inch green) it can cause severe
damage to leaves
and young canes. Lime sulfur is
recommended for control of the cane infecting fungi (anthracnose, cane
and spur blight). The delayed dormant application in spring is intended
eliminate or reduce the overwintering inoculum for these diseases on
Where cane diseases are a problem, this spray is very important. Where
sanitation is used, (old fruited and infected canes are removed from
and cane diseases are not a problem, the need for this spray may not be
necessary, or at least it would probably be safe to use the lower rate,
especially on red raspberries.
sulfur has a bad
smell (rotten eggs) so there can be a problem spraying it around your
neighbors. Some growers have received complaints from neighbors after
lime sulfur. In addition, lime sulfur is very caustic. It is harmful to
parts, paint (especially on cars) and sprayers. Special care should be
avoid drift to nontarget objects and proper protective clothing should
by the applicator.
If a dormant
of fungicide is required, and
lime sulfur cannot be used, Bordeaux mixture or a fixed copper
fungicide can be
used in its place. Although lime sulfur is the proven material, dormant
of copper should provide some level of control. The use of copper
in the growing season (after
leaves are present),
could result in significant plant damage.
Sulfur is available as a wettable powder or
flowable formulations. Sulfur is registered for control of powdery
mildew. Sulfur has little or no activity
other bramble diseases caused by fungi. Because powdery mildew is
a serious problem in the Midwest, sulfur is of little importance within
bramble disease management program.
There are several biocontrol products
control of Botrytis fruit rot. Their
efficacy under moderate to severe disease pressure needs to be